Servo mechanism for controllable pitch propellers



March 2, 1965 N. J. LIAAEN 3,171,494

SERVO MECHANISM FOR CQNTROLLABLE PITCH PROPELLERS Filed Oct. 26. 1962 2 Sheets-Sheet 1 FIG]. 102 I4 I05 ,3, 2 4

9 I62 I64- 1 3 5 2/ 22 a I I I6 I 10/ l I i I VI i J/O W ll ,7 I //l a l/ MaYCh 1955 N. J. LIAAEN 3,171,494

SERVO MECHANISM FOR CONTROLLABLE PITCH PROPELLERS Filed Oct. 26, 1962 2 Sheets-Sheet 2 |""'B 2/ F/G.4. I3/ 3 5 4 2 I4 9 24 I02 22 104 I /l0 llweumt 4770 U/EYS United States Patent M 2 Claims. ci. 170-46031) Heavily loaded controllable pitch propellers are often provided with a control mechanism which provides a couple of forces wherein the forces act on either side of the axis of rotation of each propeller blade, for the purpose of providing a sufficiently great momentum for the control of the blade. Hereby, the couple of forces act upon the individual propeller blade through a crank disc having two diametrically positioned cranks (double acting arrangement). The crank disc is journalled in the propeller-hub wall and is secured to the blade base.

Such a control mechanism, with the associated servo motor arranged in the hub has up till now entailed a complicated construction. In one construction, the rotation of the blades has been effected by means of a pair of servo cylinders arranged in the hub, one in front and one behind the axes of rotation of the blades. Each cylinder had been equipped with a double acting piston. The cylinder spaces to either side of the piston have communicated with a distribution slide in one piston rod through passages in the hub walls. The piston rods are directed against each other and are provided with slide means associated with the cranks of the crank discs, such cranks being diametrically positioned relatively to the disc axis.

In other constructions, a servo motor has been positioned in the hub behind the axes of rotation of the propeller blades. The servo motor is provided with a floating cylinder wherein the bottom which faces forwardly is provided with links or slide means associated with one set of cranks on the crank discs. The piston of the servo motor is in turn, through its piston rod and by means of links or slide means associated with the second set of cranks. The distribution slide of the servo motor may be arranged in or outside of the hub, for instance in the vessel.

It is a known phenomenon that the momentum required for the rotation of the blades of a controllable pitch propeller under operation, is the highest when the propeller blades are rotated from movement asternto move ment ahead, and considerably smaller when the blades are rotated from movement ahead to movement astern.

It is an object of the present invention to provide a simplified construction of the servo motor and the associated motion mechanism in the hub by utilizing the phenomenon referred to, thereby using a couple of forces providing oppositely directed rotational forces to each blade base, the forces of such couple of forces being, when effecting a rotation to movement ahead, acting to either side of the axis of rotation of each individual blade, whereas only one of the said forces is effective, when effecting a rotation to movement astern while the other is ineffective.

. Further features and advantages of the present invention will appear from the following description, taken together with the accompanying drawings which show two embodiments of the invention.

In the drawings,

FIGURES 1 and 4 are axial sectional views of the hub of a controllable pitch propeller, in two different embodiments of the invention.

FIGURES 2 and 5 are corresponding sectional views 3,171,494 Patented Mar. 2, 19 65 of the two hubs, taken along the lines B-B in FIGURES 1 and 4, respectively.

FIGURES 3 and 6 are views of the corresponding mechanisms, taken along the lines CC of FIGURES 2 and 5, respectively.

In all figures corresponding parts are provided with the same reference numerals.

In the FIGURES 1 to 3, 1 is the propeller shaft, provided with a flange in the aft end, to which flange the hollow hub 2 of the controllable pitch propeller is secured. 3 is one of the three propeller blades, each blade being bolted to a crank disc 4, thereby enclosing between them an annular bearing ring 21 in the wall of the hub 2. A sealing 5 is positioned around the ring 21 for the purpose of preventing water to enter into and oil to leave the hub. Each crank disc 4 is provided with a pair of cranks 6 and 7, respectively, poistioned at 180 to each other relatively to the axis of the disc 4. By means of these cranks, the blade may be rotated by means of a servo motor situated in the hub and consisting of a cylinder 8 integral with the hub or flanged on to the same. The cylinder 8 is closed at the aft end, i.e. the end remote from the axes of the blades, and is open at the opposite end, facing the space 22 of the hub.

In the aft end of the cylinder 8, a piston 9 is situated, the same being secured to a piston rod 10 carrying at its forward end a slide means 11 comprising guide members 111 and 112, and therebetween a slide block 12 which may slide along the members 111 and 112 and at the same time turn around the axis of the associated crank 6.

The cylinder 8 is also provided with a second piston 13, situated in front of the first piston 9. This second piston 13 is, at 14, in sealed, slidable connection with the piston rod 10, and is in front provided with three projections 131, one to each propeller blade. Each projection 131 is provided with a forward face 132 slidably engaging a slide block 15 which is turnably mounted on the second crank 7.

In a bore 161 in the piston rod 10 there is provided a distribution slide 16 which is supplied with pressure medium through a tube 17 arranged in a bore 110'in the shaft 1. The tube 17 may move the slide 16 axially of the hub, in the usual manner, by actuating from inside the vessel.

The slide 16 has inlet port 161 and outlet ports 162 and 163.

The slide face in the piston rod 10 is provided with ports 162 communicating with the space between the pistons 9 and 13 and ports 103 and 104 communicating with the cylinder space behind the piston 9.

In the piston rod 10, there is provided a passage i which establishes communication between the outlet port 163 of the slide and the space 22 in the hub. The slide 16 is also provided with passages 164 which, through the bore 101 in the rod 10 establish communication between the outlet port 162 and the space 22 of the hub. The space 22 is, through the bore in the shaft 1, in communication, in the usual manner, with the suction side of the pressure pump of the servo motor, through an overhead tank, not shown, above the water line of the vessel.

The arrangement shown in the FIGURES l to 3 functions in the following manner: The slide 16 is shown in its middle position. If moved slightly to the aft, i.e. to the left in the drawing, the pressure medium is flowing through the tube 17, the inlet port 161, port 102 and further on into the space between the pistons 9 and 13, which are moved away from each other, outlet being provided from the aft side of the piston 9, through the ports 103 and 163 to the passage 105 and also through the ports 104 and 162 and passage 164 to the space 22 in the hub 2,.

which i'scommunicating, through the bore 110,; with the overhead tank, as indicated above. The 'piston 9 moves the rod 10 in the aftwarfds diretion, whereby the slide guide 111 engages the slide block and'the slide block 12, in turn, engages the crank 6, FIGURE 3, jvhic'h effects drawing, establishes a pressure in the annular space between the tubes 18 and 17. Through the transverse bore 102 from the annular space between the tubes 18- and 17,

. pressure'is established in the space between the. pistons 9 a clockwise rotation of the crank disc 4. The; piston 13 a is, by the pressure prevailing in the space between the] pistons, moved forwardly, and the face 132 is forcing the: block 15 forwardly, to the effect that the crank .7 is also rotating the disc 4 in clockwise direction. propeller blades are rotated from movement 'astern to movement ahead, under the influence ofa couple of forces having one fdfce acting on eitherof the cranks 6 and 7;

If the slide 16 isdisplaced. ferwardly from the middle position shown in the drawing, the .pfessui'esmedium is passing from the port 161,. through 104 to the aft side of the piston 9, which is moved forwardly, as outlet is estab-- Thus,- the and 13, andthe pistons are moved away from each other,

the back side of the piston 9 having outlet through the tube 17. The returnof the distribution slide. is effected, for instance by actuating the front end of thetube 18 in the vessel.

Thepistons 9 and 13, which are always moving in mu-.

tually opposite directions, have their diameters-so dimensioned that no volume change is effected in' the space 22 a in the hub. This space 22 is, throughrecesses in the guide lished between the pistons 9 and 13 through the port 102- to 163 and through the bore 105 to thespace 22' of the hub 2.

When the piston 9 is moved forwardly, the piston rod 10 will, through the slide guide 112 and the block 12 and the crank 6, rotate the disc 4 in an anti-clockwise direction. The block 15 is, in this case, receiving no other infiuence than through the crank 7, and the piston 13 is moved in the aftwards direction, a. movement which is not preventedas the space between the pistons is open to the outlet (exhaust pressure). The propeller blades are rotated from movement ahead to movement astern under the sole influence of one of the forces through the crank 6, whereas the second crank 7 is notinfluenced.

During the rotation of the blades, the space 22 of the hub, is all the time placedunder exhaust pressure fromthe servo medium. This pressure is always kept higher than the water pressure surrounding the hub, due to 'the fact that the exhaust must pass an overhead tank in the ves"1 sel. The sealing 5 surrounding the blade journal is consequently not subjected to any pressure variations which might damage the sealing. q T

The FIGURES 4 to 6 illustrate a modified construction of the servomotor.

. tribution slide arranged in the hub, as the slide is mounted journals.

member 120, communicating with the bore 110 in the shaft and this bore is, in turn, communicating with an overhead tank in the vessel. In this manner the. hub is not subjected to any pressure variations, which might in the second embodiment in the provision of two such.

open cylinders 23 and 91, having a single acting piston 13, which, consequently, can transfer only forces which are I directed outwardly from the cylinder opening to thatpart of the mechanism 7 and 15 which are here influenced in one direction'only and with pressure directly. from the front side. 132. of the piston 13. V l

' The first rotation mechanism 6 and 12 includes a double acting slide means, 11 which, in conventional manner,

is influenced from the double acting piston 9.

When a 'greatmomentum is required for'the rotation of the blades, both mechanisms 13.157 and 9-10-11- In this embodiment, there is no dis- 12-6, respectively are operating;

When a smaller momentumis required, merely one of the mechanisms, viz. 940-11 -1246 is operating.

a If the cylinders of FIGURE 1 is formed withdifferent diameters, and" so that the piston 13 is cooperating with inside the vessel. The'servo-rnotor in the hub is so ar- I, ranged that no change in volume of the space ins de the hub is effected during the rotation of the blades.

In FIGURES 4 to 6, 23 is a cylinder mounted in the aft end of the hub 2 and closed at the aft end by a bottom 24. In the cylinder 23 there is provided a bell shapedpiston 9 which is secured to the piston rod 10 which, atits forward end carries the slide means 11' with the slidelrnems ber's 111 and 1 12, betweenzwhich the slide block .12 is: 'slideably mounted while being turnably mounted on the crank 6. r

' blades.

'tained,.but is also not required, 'astherearward thrust is'by far smaller than the forward thrust. I'claimr' K The bell shaped piston forms a cylinder 91in which 'a second piston 13 is arranged so as to, at 14,:be in sealed I slidable relation to the piston rod 10. 'The second piston 13 is, in front, provided with three projections 131,.one to each of the blades of the propeller. Each projection=131 is provided with a front face 132- slideably engaging the slide block 15,. which is turnably mounted on the second crank7. Y

The piston rod'10isprovidedwith ,a bore 101 and a transverse bore 102 between the pistons 9 and. 13. -111 front of the slide means '11, the piston rod is provided with an extension 103 connected to a tube 18 provided in the portion of the" biggest diameter, the crank 7 is subjected to a greater forwardly directedf'force when the pistons are moved away from each other, than the force towhich the crank 6 is subjected, This'force difference will counteract the rotational momentum to the crank discs 4 which is due to the forward pressure (thrust) onlthe.

Under movement astern, this effect is not obcontrollable pitchpropeller including a hollow hubrgtatable-about a predetermined axis, a'plurality of blades respectivelyjournalled in said hub for'pitch changing adjustment 'about'axes extending generally radially to said rotational axis, a crank disc positioned on the base of 1 each of' said blades and secured thereto at right angles to the pitch changing axis of thesaid'blade and, provided with a pair of cranks'posi tioned diametrically to the said axis,

a' slide means carried by the said crank disc and 'rotatably mountedon eachof the said cranks, a cylindermemb'er extending axially of the said hub andbeing' closed at the the shaft bore'1'10.- The piston rod portion 103 is carried in a guide member in the propeller shaft 1. i The pis:

ton rod-10 is provided with an interior tube 104 which is sealed at the outside'in the rod 10 aft of the transverse bore 102,. but forms an' annular space between the bore 101 and the tube 104' in front of the'bore 102. The tube end remote from the said crank discs and open at the end facing the said crank discs, a piston mountedfor slidable movement in the saidcylinder member and presenting a v plurality of projections extending axially of the said hub,

104 has in front a tube'extension 17 inside the tube 18. a

The arrangement shown in' the FIGURES 4'to6 functions in the following manner: A pressure medium distribution slide, situated inside-the vessel and not shown in the each such projection being in operational connectionwith the said 'slidemeansiof one of said cranks on one crank disc, a second piston mounted for slideable movement in the said cylinder member at the side of the first said piston remote from the said crank discs, and a connecting rod extending axially 'ofthe' said hub between the said second. pistonand the said crank, discs and in operational con-' nection with the said slide means of one crank on each of the said discs.

2. A controllable pitch propeller including a hollow hub rotatable about a predetermined axis, a plurality of blades respectively journalled in said hub for pitch changing adjustment about axes extending generally radially to said rotational axis, a crank disc positioned on the base of each of said blades and secured thereto at right angles to the pitch changing axis of the said blade and provided with a pair of cranks positioned diametrically to the said axis, a slide means carried by the said crank disc and rotatably mounted on each of the said cranks, a cylinder member extending axially of the said hub and being closed at the end remote from the said crank discs and open at the end facing the said crank discs, a piston mounted for slidable movement in the said cylinder member and presenting a plurality of projections extending axially of the said hub, each such projection being in operational connection with the said slide means of one of said cranks on *6 one crank disc, 21 second cylinder member extending axially of the said hub and presenting an internal cylinder surface in axial slidable engagement with an external cylinder surface on the said first cylinder member, and a connecting rod extending axially of the said hub between the closed end of the said first cylinder member and the said crank discs and in operational connection with the said slide means of one crank on each of the said discs.

References Cited in the file of this patent UNITED STATES PATENTS 2,693,243 Strandell et al Nov. 2, 1954 2,913,057 Willi Nov. 17, 1959 2,925,131 Willi Feb. 16, 1960 3,051,248 Hatcher Aug. 28, 1962 FOREIGN PATENTS 1,130,474 France Oct. 1, 1956 

1. A CONTROLLABLE PITCH PROPELLER INCLUDING A HOLLOW HUB ROTATABLE ABOUT A PREDETERMNED AXIS, A PLURALITY OF BLADES RESPECTIVELY JOURNALLED IN SAID HUB FOR PITCH CHANGING ADJUSTMENT ABOUT AXES EXTENDING GENERALLY RADIALLY TO SAID ROTATIONAL AXIS, A CRANK DISC POSITIONED ON THE BASE OF EACH OF SAID BLADES AND SECURED THERETO AT RIGHT ANGLES TO THE PITCH CHANGING AXIS OF THE SAID BLADE AND PROVIDED WITH A PAIR OF CRANKS POSITIONED DIAMETRICALLY TO SAID AXIS, A SLIDE MEANS CARRIED BY THE SAID CRANK DISC AND ROTATABLY MOUNTED ON EACH OF THE SAID CRANKS, A CYLINDER MEMBER EXTENDING AXIALLY OF THE SAID HUB AND BEING CLOSED AT THE END REMOTE FROM THE SAID CRANK DISCS AND OPEN AT THE END FACING THE SAID CRANK DISCS, A PISTON MOUNTED FOR SLIDABLE MOVEMENT IN THE SAID CYLINDER MEMBER AND PRESENTING A PLURALITY OF PROJECTIONS EXTENDING AXIALLY OF THE SAID HUB, EACH SUCH PROJECTION BEING IN OPERATIONAL CONNECTION WITH THE SAID SLIDE MEANS OF ONE OF SAID CRANKS ON ONE CRANK DISC, A SECOND PISTON MOUNTED FOR SLIDEABLE MOVEMENT IN THE SAID CYLINDER MEMBER AT THE SIDE OF THE FIRST SAID PISTON REMOTE FROM THE SAID CRANK DISCS, AND A CONNECTING ROD EXTENDING AXIALLY OF THE SAID HUB BETWEEN THE SAID SECOND PISTON AND THE SAID CRANK DISCS AND IN OPERATIONAL CONNECTION WITH THE SAID SLIDE MEANS OF ONE CRANK ON EACH OF THE SAID DISCS. 